Martin D. Ginsburg, 78, a Georgetown University tax law professor whose blind date more than a half-century ago with a quiet undergraduate named Ruth Bader blossomed into an enduring marriage, died June 27 of complications from metastatic cancer at his home in Washington.

Mr. Ginsburg joined the Georgetown faculty in 1980 and was considered one of the nation's preeminent tax-law experts for his mastery of the Internal Revenue Code's intricacies. He also served as the sounding board, moral supporter and intellectual sparring partner for his wife, Ruth Bader Ginsburg, as she rose to become history's second female Supreme Court justice.

The couple celebrated their 56th wedding anniversary on June 23. The foundation of their relationship, they both said, was mutual respect and equality -- and a willingness to share domestic duties.

Soon after their wedding, young Army Lt. Ginsburg was assigned to an artillery unit at Fort Sill, Okla. One night, Mrs. Ginsburg presented her husband with a dish he immediately deemed inedible, he later told The Washington Post.

"What is it?" he asked.

"It's tuna fish casserole," she replied.

From then on, Mr. Ginsburg took over responsibility for dinner, finding inspiration in an English translation of an Escoffier cookbook that had been a wedding gift.

"As a general rule," Mr. Ginsburg told the New York Times in 1997, "my wife does not give me any advice about cooking, and I do not give her advice about the law. This seems to work quite well on both sides."

Martin David Ginsburg was born June 10, 1932 in Brooklyn, N.Y., and grew up in Rockville Centre on Long Island. His father was vice president of the Federated department store chain.

He went to Cornell University in New York, where he studied chemistry. His roommate set him up on a blind date with Ruth Bader. Later, she recalled that Mr. Ginsburg, a gregarious varsity golf player, was "the only young man I dated who cared that I had a brain."

He received a bachelor's degree from Cornell in 1953, and the Ginsburgs were married in a small ceremony shortly after her graduation a year later. That day, Mr. Ginsburg's mother approached the bride and took her hand."I am going to give you some advice that will serve you well," the mother-in-law said. "In every good marriage, it pays sometimes to be a little deaf." As she spoke, she placed a set of wax ear plugs in Mrs. Ginsburg's palm.

"I have recalled that advice regularly," Mrs. Ginsburg wrote in a 2002 anthology of essays, "The Right Words at the Right Time," edited by Marlo Thomas. "Tempers momentarily aroused generally subside like a summer storm."

Not long after their wedding, the couple headed to Fort Sill. In a 1993 interview with The Post, Mr. Ginsburg recalled that his military career got off to a slow start.

"How much experience have you had in artillery?" a captain asked upon Mr. Ginsburg's arrival.

"I will level with you," Mr. Ginsburg said. "The first artillery piece I have ever seen in my life is the one I see through your window, on the back of that jeep."

The captain replied: "Son, that's an automatic fence post digger."

After his Army service, Mr. Ginsburg and his wife attended law school at Harvard University.

He graduated in 1958 and joined the New York firm Weil, Gotshal & Manges. Mrs. Ginsburg left Harvard and finished law school at Columbia University to be closer to her husband.

Mr. Ginsburg practiced tax law in New York and was an adjunct law professor at New York University until deciding in 1978 to pursue teaching full time. He joined the faculty at Columbia's law school and moved to Georgetown in 1980 after Mrs. Ginsburg became an appellate judge in Washington. He continued to practice as a tax lawyer at Fried, Frank, Harris, Shriver & Jacobson in the District.

He was co-author of "Mergers, Acquisitions, and Buyouts," a tax law treatise updated semiannually.

In 1984, Mr. Ginsburg helped Ross Perot resolve tax problems involving the acquisition of his company, Electronic Data Systems, by General Motors. Mr. Ginsburg refused to accept payment from Perot for his efforts. Instead, Perot endowed a chair at the Georgetown law school in Mr. Ginsburg's honor.

Besides his wife, survivors include two children, Jane Carol Ginsburg of New York and James Steven Ginsburg of Chicago; a brother; a sister; and four grandchildren.

Mr. Ginsburg said he was proud of his wife's accomplishments and had no regrets about the compromises they made for each other.

"I have been supportive of my wife since the beginning of time, and she has been supportive of me," Mr. Ginsburg told the Times in 1993. "It's not sacrifice; it's family."